Christine Negroni riffs on aviation and travel and whatever else inspires her to put words to page.

Saturday, December 29, 2012

Fatality Statistics Meaningless as Safety Measure

As certain as the ball will drop in New York's Times Square on Monday midnight, there will be a round of news stories summing up 2012 in terms of aviation safety. Oh wait a minute, it's already started.

"Overall, it was certainly the safest year ever," Paul Hayes told UPI.com. Hayes is the director of safety at Ascend, a consulting firm, that specializes in the commercial and financial aspects of aviation.

I've got no problem with good news, or with the numbers that Hayes and Ascend present. The problem is the meaninglessness of the particular criteria used. Ascend is restricting its safety data to accidents with fatalities.

In the vast majority of aviation accidents, nobody dies. When the National Transportation Safety Board did an in depth statistical study 10 years ago, the survival rate in reportable accidents was 95%. If that surprises most people, and I suspect it does, Arnold Barnett, a professor of statistics at the Massachsetts Institute of Technology can explain why. "The events that make the greatest impression are the ones that involve fatalities," he said.

To the general public, airplane accident brings to mind the
scene from Denzel Washington's new movie Flight, in which a plane
smashes to earth trailing tongues of fire. But an accident is also
an aborted takeoff and a runway overrun, an in-flight upset and a structural failure. Turbulence and plane to plane collisions are also accidents and while
people can be injured seriously, all this mayhem is not in the
statistics Ascend is feeding to reporters as it raves enthusiastically about
the safest year ever in aviation.

When safety is measured by an absence of fatalities, the significance of non lethal events is diminished even though most safety specialists think these percursors are the most indicative of an overall safety culture. A preventive approach to reducing risk is so important commercial operators in most parts of the world are required to have safety management systems.

Several years ago, at the International Society of Air Safety Investigators annual seminar, the entire three day program was dedicated not to presentations on the big accident investigations, but on how to better probe the little ones. "Our biggest opportunity to make things better is before someone dies," one participant told me.